diff --git a/qubesmanager/create_new_vm.py b/qubesmanager/create_new_vm.py
index 97bba22b..6e7fa52f 100644
--- a/qubesmanager/create_new_vm.py
+++ b/qubesmanager/create_new_vm.py
@@ -71,7 +71,7 @@ def __init__(self, qtapp, app, parent=None):
             allow_internal=False, allow_default=True, allow_none=True)
 
         self.name.setValidator(QtGui.QRegExpValidator(
-            QtCore.QRegExp("[a-zA-Z0-9-]*", QtCore.Qt.CaseInsensitive), None))
+            QtCore.QRegExp("[a-zA-Z0-9_-]*", QtCore.Qt.CaseInsensitive), None))
         self.name.selectAll()
         self.name.setFocus()
 
diff --git a/qubesmanager/qube_manager.py b/qubesmanager/qube_manager.py
index 6cec676b..7d8931c4 100644
--- a/qubesmanager/qube_manager.py
+++ b/qubesmanager/qube_manager.py
@@ -263,7 +263,7 @@ def __init__(self, qt_app, qubes_app, parent=None):
 
         self.searchbox = SearchBox()
         self.searchbox.setValidator(QtGui.QRegExpValidator(
-            QtCore.QRegExp("[a-zA-Z0-9-]*", QtCore.Qt.CaseInsensitive), None))
+            QtCore.QRegExp("[a-zA-Z0-9_-]*", QtCore.Qt.CaseInsensitive), None))
         self.searchContainer.addWidget(self.searchbox)
 
         self.connect(self.table, QtCore.SIGNAL("itemSelectionChanged()"),
diff --git a/qubesmanager/settings.py b/qubesmanager/settings.py
index f71611e0..9de9baa0 100755
--- a/qubesmanager/settings.py
+++ b/qubesmanager/settings.py
@@ -294,7 +294,7 @@ def __init_basic_tab__(self):
         self.vmname.setText(self.vm.name)
         self.vmname.setValidator(
             QtGui.QRegExpValidator(
-                QtCore.QRegExp("[a-zA-Z0-9-]*",
+                QtCore.QRegExp("[a-zA-Z0-9_-]*",
                                QtCore.Qt.CaseInsensitive), None))
         self.vmname.setEnabled(False)
         self.rename_vm_button.setEnabled(not self.vm.is_running())